Electric fuse for elevated circuit voltages

ABSTRACT

An electric fuse having plug terminals conductively interconnected by fuse links has means forming part of the plug terminals and performing the dual function of (1) forming lugs for conductively connecting the fuse links to the plug terminals and of (2) positively positioning the ends of the fuse links relative to the plug terminals preparatory to establishing the aforementioned conductive connection between the fuse links and the plug terminals.

Umted States Patent [1 1 [111 3,777,297 pp, J L4 Dec. 4, 1973 [54] ELECTRIC FUSE FOR ELEVATED CIRCUIT 2,223,959 12/ 1940 Lohausen 337/161 X VOLTAGES FOREIGN PATENTS OR APPLICATIONS [75] Inventor: E a 33 601,884 5/1948 Great Britain 337/l6l ew urypor ass.

[73] Assignee: The Chase-Shawmut Company, Primary ExaminerBernard A. Gilheany Newburyport, Mass. Assistant Examiner-F. E. Bell 22 Filed: Oct. 27, 1972 21 A l. N 301 5 1 pp 0 6 57 ABSTRACT [52] U S Cl 337/161 An electric fuse having plug terminals conductively [51] 85/12 interconnected by fuse links has means forming part [58] Field 164 180 of the plug terminals and performing the dual function 229 of (l) forming lugs for conductively connecting the fuse links to the plug terminals and of (2) positively 5 Referenes Cited positioning the ends of the fuse links relative to the plug terminals preparatory to establishing the afore- UNITED STATES PATENTS mentioned conductive connection between the fuse 3,400,235 9/1968 Howard et al. 337/I6I X links and the terminals 2,382,271 8/1945 Suits et al. l 337/l6l X 2,667,549 1/1954 Fahnde et a1. 337/161 9 Claims, 5 Drawing Figures k\}\\ o 6 1o .4. 12

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BACKGROUND OF THE INVENTION This invention relates to fuses for elevated circuit voltages, e.g., -15 Kv, and particularly to fuses whose terminal elements are formed by terminal plugs. One of the most important applications of this invention are fuses wherein an insulating mandrel for supportingthe fusible element is dispensed with. Fuses for elevated circuit voltages wherein an insulating mandrel or support for the fuse links is dispensed with are, for instance, disclosed in US Pat. No. 3,611,239 to Frederick J. Kozacka, Oct. 5, 1971 for HIGH-VOLTAGE FUSE HAVING INNER CORE AND OUTER SHELL FUSE LINKS. According to that patent the ends of the fuse links are angularly bent to L-shape-forrn and screwed against the axially inner end surfaces of the plug terminals and also connected by solder joints to said radially inner end surfaces. This structure performs very satisfactorily, but its manufacture involves relatively much time of skilled labor. It is, therefore, one object of this invention to provide fuses having conductive connections between fuse links and plug terminals performing as well as those disclosed in the above patent, but being considerably easier to establish.

The copending patent application of Erwin Salzer, filed 7/9/71, Ser. No. 161,089 for METHOD OF AS- SEMBLING HIGH-VOLTAGE FUSES AND SUB- ASSEMBLY THEREFOR discloses another type of fuses for elevated circuit voltages wherein an insulating support for the fusible element is eliminated or dispensed with. The structure of Salzer involves one or more ribbon fuse links which are helically wound, arranged inside the casing in coaxial relation thereto, but not supported by a center post or supporting mandrel as shown, for instance, in US. Pat. No. 2,417,268 to A.H. Powell, March 1 1, 1947 for INDICATING MEANS FOR THERMAL CIRCUIT INTERRUPT- ERS. Wherever helically wound insulating-coresupported fusible elements are used in a fuse for elevated circuit voltages, the'insulating core is generally suppliednear both ends thereof with a pair of annular conductor means to which the ends of the fusible elements are conductively connected and which, in turn, are conductively connected to the terminal elements of the fuse. This conventional design principle'lends itself to fuse structures provided with terminal caps, as shown in the above Powell patent, but not to fuses having plug terminals, as shown in the above Ko zacka patent, and in the above copending Salzer patent application. It is, therefore, one of the objects of this invention to provide means having the above referred-to two functions and applicable to fuses for elevated circuit voltages having plug terminals irrespective of whether the fuse links thereof are substantially straight, substantially zig-zag shaped, or substantially in the form of a helix.

SUMMARY OF THE INVENTION Fuses embodying this invention include a tubular casing of electric insulating material and a body of pulverulent arc-quenching filler inside the casing. A plurality of fuse link means inside the casing is embedded in said pulverulent arc-quenching filler. A pair of plug terminals is fitted into the ends of the casing, closing the latter. Each of said pair of plug terminals has a coaxial collar on the axially inner end surface thereof. Said collar of each of said pair of plug terminals has a plurality of angularly displaced relatively small substantially radial apertures each receiving one of the ends of one of said plurality of fuse link means, and each further receiving a solder joint conductively connecting said one of the ends of said plurality of fuse link means to one of said pair of plug terminals. Said collar of each of said pair of plug terminals further has a plurality of relatively large, substantially radial apertures establishing open passageways between the space radially inside and the space radially outside said collar. Portions of said body of pulverulent arc-quenching filler fill said relatively large apertures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is substantially a longitudinal section of a fuse embodying the present invention taken along 1-1 of FIG. 2, the center portion of the fuse being broken away, and some of the constituent parts thereof being shown in elevation rather than sectionalized;

FIG. 2 is a section along 2-2 of FIG. 1;

FIG. 3 is an illustration similar to FIG. I of one end of a fuse which is a modification of the structure of FIGS. 1 and 2 (the other end being deleted in FIG. 3 since it is supposed to be identical with the end shown);

FIG. 4 is a section along 4-4 of FIG. 3; and FIG. 5 is a front view of a part of the structure of FIGS. 3 and 4.

DESCRIPTION OF PREFERRED EMBODIMENTS In FIGS. 1 and 2 reference numeral 1 has been applied to indicate a tubular casing of an electric insulating material, e.g., a melamine glass-cloth-laminate. Case 1 contains a pulverulent arc-quenching filler 2, preferably quartz sand. The structure further includes a plurality of ribbon fuse link means 3 or, to be more specific, six ribbon fuse links 3 embedded in tiller 2. Each fuse link 3 supports one or more beads 4 of electric insulating material. These beads are preferably manufactured in accordance with the teachings of the .copending patent applications of Frederick J. Kozacka,

filed 5-4-72, Ser. No. 250,175 for HIGH-VOLTAGE FUSE HAVING FULL RANGE CLEARING ABIL- ITY. Each fuse link 3 has semicircular bends to both sides of beads 4 to preclude displacement of beads 4 in a direction longitudinally of fusible elements 3. The metallic plug terminals 5 are fitted into the ends of casing 1, closing the latter. Steel pins 6 project transversely through casing 1 into plug terminals 5, firmly affixing the latter to the former. Each plug terminal 3 has a coaxial collar 7 projecting from the axially inner end surface thereof. Collar 7 of each plug terminal 5 has a plurality of angularly displaced, relatively small, substantially radial apertures 8. As is apparent from FIG. 2, the angular displacement of apertures 8 may be 60, and the number of apertures 8 equal to the number of fuse links, e.g., six. The axially outer ends of fuse links 3 are bent at about right angles forming hooks which are inserted into apertures 8. This is a convenient means for properly positioning fuse links 3. After the fuse links 3 are positioned in this fashion each of apertures 8 receives a'solder joint conductively connecting the bent hook-shaped ends of fuse links 3 to collars 7 and terminal plugs 5. In the interest of clarity these solder joints have not been shown in the drawings. The width of fuse links 3 may exceed the diameter of apertures 8 in collars 7. If this is the case each link 3 is provided with end tabs of decreased width adapted for insertion into apertures 8. This has been indicated in FIG. 2 and has been shown more clearly in FIGS. 3 and 4. Collars 7 of plug terminals are further provided with a plurality of angularly displaced, relatively large,-substantially radial apertures9 (FIG. 2). Apertures 9 alternate with apertures 8. The former establish passageways between the spaces radially inside and the spaces 11 radially outside collars 7. Portions of the body 2 of pulverulent arc-quenching filler fill the apertures 9. Plug terminals 5 are provided in the centers thereof with screw-threaded bores closed by hex screws 12 when the fuse structure is fully assembled. One of screws 12 may be deleted, if desired. A blown fuse indicator as disclosed and claimed in US. Pat. No. 3,621,433 to Richard A. Belcher, Nov. 16, I971 for ELECTRIC CARTRIDGE FUSE HAVING PLUG TERMINALS may be substituted for one of the screws 12.

The screw-threaded bores in plug terminals 5 are intended to space plug terminals 5 temporarily during the assembly process of the fuse, as disclosed in detail in US. Pat. No. 2,740,187 to P.C.Jacobs et al., Apr. 3, 1956 for METHOD OF ASSEMBLING FUSES. The fuse is filled with pulverulent arc-quenching filler through one of the screw-threaded bores in the plug terminals 5, subsequently closed by one of screws 12. The arc-quenching filler forms a center jet when filled into casing l which is allowed to readily spread out radially by virtue of the presence of large apertures 9 in collars 7 of plug terminals 5. Because of the presence of collars 7 a proper filling operation could not be performed in the absence of apertues 9.

In FIGS. 3 to 5 the same numerals as in FIGS. 1 and 2 with a prime added have been applied to indicate like parts. Thus tubular casing l' of insulating material contains a body 2 of pulverulent arc-quenching filler in which six ribbon fuse links 3 are embedded. The terminal plugs 5 of which but one is shown in FIG. 4 are press-fitted into the ends of casing l and firmly held in position bysteel pins 6. The plug terminals 5 are provided on the axially inner end surfaces thereof with coaxial grooves 13'. A collar 7 is formed in each plug terminal 5 by a strip of sheet metal which is inserted edgewise into its groove 13'. The collar-forming strips 7' of sheet metal are bent annularly to fit into grooves 13. One such strip is shown in FIG. Sprior to bending thereof, i.e., upon having been formed by a blanking or stamping operation. Collars 7' are preferably conductively connected to the plug terminals 5 proper by solder joints (not shown). Collars 7' have small holes 8' into which the ends of fuse links 3' are inserted. At the point of insertion the width of fuse links 3 is reduced to form tabs of reduced width which can readily be inserted into small apertures 8 and are soldered to collars 8 by means of solder joints not shown in FIGS. 3 and 4. Collars 5' are further provided with angularly displaced relatively large substantially radial apertures 9 establishing passageways between the spaces 10 radially inside and the spaces 11' radially outside collars 7. These apertures allow the arc-quenching filler 2 to flow radially outwardly from spaces 10 to spaces 11 during the filling process of the fuse, as explained above in connection with FIGS. 1 and 2. i

In the structure of FIGS. 1 and 2 each of plug terminals 5 andthe collar 7 thereof is formed by a single integral workpiece. This may be produced by machining. Preferably such an integral workpiece 5,7 is formed by sintered metal.

It has been found that the collar 7,7 on the plug terminal 5,5 through which casing 1,1 is filled with filler 2,2 must be provided with the larger apertures 9,9 to achieve complete and satisfactory filling of the fuse. The collars 7,7 of the plug terminals 5,5 on the opposite end of the casing 1,1 must not necessarily be provided with the large apertures 9,9. It is, however, desirable to have identical plug terminals 5,5 with identical collars 7,7 on both ends of the fuse rather than different plug terminals on each end thereof.

As shown in FIG. 1 each collar 7 may have two tiers, or levels, each having relatively small apertures, or bores, for insertion into it of one end of fuse links 3 and for receiving a solder joint conductively connecting the particular end of a fuse link 3 to the plug terminal 5. This arrangement makes it possible to vary at will the position of fuse links 3 relative to casing l or the radial spacing of fuse links 3 from the axis of casing 1. This arrangement makes it further possible to provide fuses having a radially inner shell of ribbon fuse links and a radially outer shell of ribbon fuse links. Whatever arrangement of fuse links 3,3 is selected, the small apertures in collars 7,7 make it possible to precisely and firmly locate fuse links 3,3 when assembling the fuse. As suggested above the bent ends of fuse links 3,3 may be consdiered to be hooks pushed into holes to locate the fuse links 3,3 prior to forming solder joints. The number of link-receiving small apertures in collars 7,7 is preferably relatively large, thus allowing to establish with identical plug terminals 5,5 various fuse link configurations involving different numbers of fuse links. The number of link-receiving small apertures in each collar 7,7 is preferably larger than shown in the drawings and may, for instance, be twelve.

I claim as my invention:

1. An electric fuse including a. atubular casing of an electric insulating material;

b. a body of pulverulent arc-quenching filler inside said casing;

c. a plurality of fuse link means inside said casing embedded in said pulverulent arc-quenching filler; and

d. a pair of plug terminals fitted into the ends of and closing said casing, each of said pair of plug terminals having a coaxial collar projecting from the axially inner end surface thereof, said collar of each of said pair of plug terminals having a plurallity of angularly displaced relatively small substantially radial apertures each receiving one of the ends of one of said plurality of fuse link means, and each further receiving a solder joint conductively con necting said one of the ends of said plurality of fuse link means to one of said pair of plug terminals, and said collar of each of said pair of plug terminals further having a plurality of angularly displaced relatively large substantially radial apertures establishing passageways between the spaces radially inside and the spaces radially outside of said collar, and

" portions of said body of pulverulent arc-quenching filler filling said relatively large apertures.

2. An electric fuse as specified in claim 1 wherein each of said pair of plug terminals and said collar thereof are formed by one single integral workpiece.

3. An electric fuse as specified in claim 1 wherein each of said pair of plug terminals is provided with an annular groove atthe axially inner end surface thereof, and wherein said collar of each of said pair of plug terminals is formed by a perforated annularly bent strip of sheet metal inserted edgewise into said groove.

4. An electric fuse as specified in claim 1 wherein said relatively small apertures and said relatively large apertures alternate.

5. An electric fuse as specified in claim 2 wherein each of said pair of plug terminals and said collar thereof are formed by one single integral workpiece of sintered metal.

6. An electric fuse including a. a tubular casing of electric insulating material;

b. a body of pulverulent arc-quenching filler inside said casing;

c. a plurality of fuse link means inside said casing embedded in said pulverulent arc-quenching filler and wholly supported by said arc-quenching filler under exclusion of any insulating supporting mandrel for said plurality of fuse link means; and

d. a pair of plug terminals fitted into the ends of and closing said casing, each of said pair of plug terminals having a coaxial integral collar on the axially inner end surface thereof, said collar of each of said pair of plug terminals having a plurality of angularly displaced relatively small apertures each receiving one of the ends of one of said plurality of fuse link means, said one of the ends of said plurality of fuse link means being conductively connected to said collar of each of said pair of plug terminals substantially at the points where said relatively small apertures are located, and said collar of each of said pair of plug terminals further having a plurality of angularly displaced relatively large apertures establishing passageways between the spaces radially inside and the spaces radially outside of said collar, portions of said body of pulverulent arc-quenching filler filling said relatively large apertures.

7. An electric fuse as specified in claim 6 wherein said relatively small apertures and-said relatively large apertures alternate, and wherein each of said pair of plug terminals and said collar thereof are formed by one single integral workpiece.

8. An electric fuse as specified in claim 6 wherein each of said pair of plug terminals is provided with an annular groove at the axially inner end surface thereof, wherein said collar of each of said pair of plug terminals is formed by a pair of annularly bent strips of sheet metal inserted edgewise into said groove, and wherein each of said strips of each of said pair of plug terminals is provided with alternating relatively small apertures and relatively large apertures.

9. An electric fuse including a. a tubular casing of electric insulating material;

b. a body of pulverulent arc-quenching filler inside said casing;

c. a plurality of ribbon fuse link means inside said casing embedded in said pulverulent arc-quenching filler; and

d. a pair of plug terminals fitted into the ends of and closing said casing, each of said pair of plug terminals having a coaxial collar projecting from the axially inner end surface thereof, said collar of each of said pair of plug terminals having a plurality of angularly displaced relatively small substantially radial apertures each receiving one of the ends of one of said plurality of ribbon fuse link means and each further receiving a solder joint conductively connecting said one of the ends of said plurality of ribbon fuse link means to one of said pair of plug terminals, and said collar of at least one of said pair of plug terminals having a plurality of angularly displaced relatively large substantially radial apertures. 

1. An electric fuse including a. a tubular casing of an electric insulating material; b. a body of pulverulent arc-quenching filler inside said casing; c. a plurality of fuse link means inside said casing embedded in said pulverulent arc-quenching filler; and d. a pair of plug terminals fitted into the ends of and closing said casing, each of said pair of plug terminals having a coaxial collar projecting from the axially inner end surface thereof, said collar of each of said pair of plug terminals having a plurallity of angularly displaced relatively small substantially radial apertures each receiving one of the ends of one of said plurality of fuse link means, and each further receiving a solder joint conductively connecting said one of the ends of said plurality of fuse link means to one of said pair of plug terminals, and said collar of each of said pair of plug terminals further having a plurality of angularly displaced relatively large substantially radial apertures establishing passageways between the spaces radially inside and the spaces radially outside of said collar, and portions of said body of pulverulent arc-quenching filler filling said relatively large apertures.
 2. An electric fuse as specified in claim 1 wherein each of said pair of plug terminals and said collar thereof are formed by one single integral workpiece.
 3. An electric fuse as specified in claim 1 wherein each of said pair of plug terminals is provided with an annular groove at the axially inner end surface thereof, and wherein said collar of each of said pair of plug terminals is formed by a perforated annularly bent strip of sheet metal inserted edgewise into said groove.
 4. An electric fuse as specified in claim 1 wherein said relatively small apertures and said relatively large apertures alternate.
 5. An electric fuse as specified in claim 2 wherein each of said pair of plug terminals and said collar thereof are formed by one single integral workpiece of sintered metal.
 6. An electric fuse including a. a tubular casing of electric insulating material; b. a body of pulverulent arc-quenching filler inside said casing; c. a plurality of fuse link means inside said casing embedded in said pulverulent arc-quenching Filler and wholly supported by said arc-quenching filler under exclusion of any insulating supporting mandrel for said plurality of fuse link means; and d. a pair of plug terminals fitted into the ends of and closing said casing, each of said pair of plug terminals having a coaxial integral collar on the axially inner end surface thereof, said collar of each of said pair of plug terminals having a plurality of angularly displaced relatively small apertures each receiving one of the ends of one of said plurality of fuse link means, said one of the ends of said plurality of fuse link means being conductively connected to said collar of each of said pair of plug terminals substantially at the points where said relatively small apertures are located, and said collar of each of said pair of plug terminals further having a plurality of angularly displaced relatively large apertures establishing passageways between the spaces radially inside and the spaces radially outside of said collar, portions of said body of pulverulent arc-quenching filler filling said relatively large apertures.
 7. An electric fuse as specified in claim 6 wherein said relatively small apertures and said relatively large apertures alternate, and wherein each of said pair of plug terminals and said collar thereof are formed by one single integral workpiece.
 8. An electric fuse as specified in claim 6 wherein each of said pair of plug terminals is provided with an annular groove at the axially inner end surface thereof, wherein said collar of each of said pair of plug terminals is formed by a pair of annularly bent strips of sheet metal inserted edgewise into said groove, and wherein each of said strips of each of said pair of plug terminals is provided with alternating relatively small apertures and relatively large apertures.
 9. An electric fuse including a. a tubular casing of electric insulating material; b. a body of pulverulent arc-quenching filler inside said casing; c. a plurality of ribbon fuse link means inside said casing embedded in said pulverulent arc-quenching filler; and d. a pair of plug terminals fitted into the ends of and closing said casing, each of said pair of plug terminals having a coaxial collar projecting from the axially inner end surface thereof, said collar of each of said pair of plug terminals having a plurality of angularly displaced relatively small substantially radial apertures each receiving one of the ends of one of said plurality of ribbon fuse link means and each further receiving a solder joint conductively connecting said one of the ends of said plurality of ribbon fuse link means to one of said pair of plug terminals, and said collar of at least one of said pair of plug terminals having a plurality of angularly displaced relatively large substantially radial apertures. 